The present invention relates to thermally-stable diamond compacts and more particularly to the production of thermally stable, dense, electrically conductive diamond compacts.
Well-known in the superabrasive art are compacts of polycrystalline abrasive particles typified by polycrystalline diamond and polycrystalline cubic boron nitride (CBN) compacts. Such compacts are represented by U.S. Pat. Nos. 3,745,623 and 3,608,818 with respect to polycrystalline diamond compacts and U.S. Pat. Nos. 3,767,371 and 3,743,489 with respect to polycrystalline CBN compacts. While such polycrystalline compacts represent a significant contribution to the art and many fields of use, thermal degradation at an elevated temperature, e.g. above about 700.degree. C., limited their usefulness, especially in metal matrix bond applications. Thermal stability of such polycrystalline compacts was improved with the advent of thermally-stable, porous self-bonded polycrystalline diamond and CBN compacts containing less than 3% non-diamond phase, hereinafter termed "porous compacts". Compacts of this type are the subject of U.S. Pat. Nos. 4,224,380 and 4,288,248.
European patent publication No. 116,403 describes a thermally-stable diamond compact comprising a mass of diamond particles present in an amount of 80% to 90% by volume of the compact and a second phase present in an amount of 10% to 20% by volume of the compact, the mass of diamond particles containing substantially diamond-to-diamond bonding to form a coherent skeletal mass and the second phase containing nickel and silicon, the nickel being in the form of nickel and/or nickel silicide and the silicon being in the form of silicon, silicon carbide, and/or nickel silicide. British Patent Application No. 8,508,295 describes a thermally-stable diamond compact comprising a mass of diamond particles present in an amount of 80% to 90% by volume of the compact and the second phase present in an amount of 10% to 20% by volume of the compact, the mass of diamond particles containing substantially diamond-to-diamond bonding to form a coherent skeletal mass and a second phase consisting of silicon, the silicon being in the form of silicon and/or silicon carbide.
Silicon-bonded polycrystalline diamond compacts also have been formed by a process which utilizes a partial vacuum for infiltrating fluid silicon into a mass of discrete diamond or CBN crystals, as disclosed in U.S. Pat. No. 4,224,455. Somewhat similar processes are disclosed in U.S. Pat. Nos. 4,238,433 and 4,242,106. An improvement to such fabrication technique is disclosed in U.S. Pat. No. 4,381,271 wherein a substantially uniform mixture of diamond or CBN crystals and fibrous graphite are infiltrated with fluid silicon under a particle vacuum under a temperature above 1004.degree. C., wherein the fibrous graphite has been subjected to a heat treatment operation under vacuum at a temperature of between about 800.degree. and 1700.degree. C.
Despite the thermal stability achieved by porous compacts and silicon-infiltrated compacts, neither product can be cut or shaped except by laser burning. Laser burning does not give the edge quality needed for many applications and laser burning equipment is not readily available to tool makers.